Broken Bolt

Hi all, '75 model. When trying to adjust the angle of the driver's seat back by backing out on the adjuster bolt that is threaded into the bottom seat frame it broke off in the weldnut. Rusted solid. I removed the seat and have been squirting Liquid Wrench and PB Blaster on the broken bolt, from the underside, for 3 days now and so far have been unable to back it out with jam-nuts. I'm in no hurry, but any ideas other than trying to drill it out ? If I take a torch to the broken bolt I will set the foam and leather on fire ! If I don't have good luck, are the left and right seats interchangeable by swapping the seat forward/rearward adjuster rails ? TIA. Oh yes, the left and right seat backs were bobbed by the previous owner in '76 because his wife was short so I don't have to worry about differences in shoulder harness channels etc.